Filter regeneration using filter temperature modulation

ABSTRACT

According to one embodiment, an apparatus for controlling the regeneration of a particulate filter of an internal combustion engine system includes an operating conditions module that is configured to monitor at least one engine system condition. The apparatus also includes a regeneration module that is configured to trigger a regeneration event if the at least one engine system condition meets a threshold. Further, the apparatus includes a thermal management module that is configured to operate the internal combustion engine system in a thermal management mode for a first time period while a regeneration event is triggered by the regeneration module. Also, the apparatus includes a high NO x  module configured to operate the internal combustion engine system in a high NO x  mode for a second time period following the first time period while the regeneration event is triggered by the regeneration module.

FIELD

This disclosure relates to exhaust after-treatment systems for internal combustion engines, and more particularly to controlling regeneration events on a diesel particulate filter (DPF) of an exhaust after-treatment system.

BACKGROUND

Emissions regulations for internal combustion engines have become more stringent over recent years. Environmental concerns have motivated the implementation of stricter emission requirements for internal combustion engines throughout much of the world. Governmental agencies, such as the Environmental Protection Agency (EPA) in the United States, carefully monitor the emission quality of engines and set acceptable emission standards, to which all engines must comply. Generally, emission requirements vary according to engine type. Emission tests for compression-ignition (diesel) engines typically monitor the release of diesel particulate matter (PM), nitrogen oxides (NO_(x)), and unburned hydrocarbons (UHC). Catalytic converters (e.g., oxidation catalysts) implemented in an exhaust gas after-treatment system have been used to eliminate many of the pollutants present in exhaust gas. However, to remove diesel particulate matter, typically a diesel particulate filter (DPF) must be installed downstream from a catalytic converter, or in conjunction with a catalytic converter. Additionally, some DPFs can have catalytic characteristics to assist in the oxidation of nitrogen oxide (NO), while other DPFs do not have catalytic characteristics.

A common DPF includes a porous ceramic matrix with parallel passageways through which exhaust gas passes. Particulate matter subsequently accumulates on the surface of the filter, creating a buildup which must eventually be removed to prevent obstruction of the exhaust gas flow. Common forms of particulate matter are ash and soot. Ash, typically a residue of burnt engine oil, is substantially incombustible and builds slowly within the filter. Soot, chiefly composed of carbon, results from incomplete combustion of fuel and generally comprises a large percentage of particulate matter buildup. Various conditions, including, but not limited to, engine operating conditions, mileage, driving style, terrain, etc., affect the rate at which particulate matter accumulates within a diesel particulate filter.

Accumulation of particulate matter typically causes backpressure within the exhaust system. Excessive backpressure on the engine can degrade engine performance (e.g., lower power and efficiency), and in some cases may result in engine stall. Particulate matter, in general, oxidizes in the presence of nitric oxides (particularly NO₂) at modest temperatures, or in the presence of oxygen at higher temperatures. If too much particulate matter has accumulated when oxidation begins, the oxidation rate may get high enough to cause an uncontrolled temperature excursion. The resulting heat can destroy the filter and damage surrounding structures. Furthermore, recovery or replacement of the filter can be an expensive process.

To prevent potentially hazardous situations, accumulated particulate matter is commonly oxidized and removed in a controlled regeneration process before excessive levels have accumulated. For oxidation of the accumulated particulate matter, exhaust gas temperatures generally must exceed the temperatures typically reached at the filter inlet. Consequently, additional methods to initiate regeneration of a diesel particulate filter may be used. In one method, a reactant, such as diesel fuel, is introduced into an exhaust after-treatment system to initiate oxidation of particulate buildup and to increase the temperature of the filter. A filter regeneration event occurs when substantial amounts of soot are consumed on the particulate filter.

A controlled regeneration can be initiated by the engine's control system when a predetermined amount of particulate has accumulated on the filter, when a predetermined time of engine operation has passed, or when the vehicle has driven a predetermined number of miles. Oxidation from oxygen (O₂) generally occurs on the filter at temperatures above about 500 degrees centigrade (° C.), while oxidation from NO₂, sometimes referred to herein as noxidation, generally occurs at temperatures between about 300° C. and 500° C. Controlled or active regeneration typically consists of driving the filter temperature up to O₂ oxidation temperature levels for a predetermined time period such that oxidation of soot accumulated on the filter takes place.

A controlled regeneration can become uncontrolled if the oxidation process drives the temperature of the filter upwards more than is anticipated or desired, sometimes to the point beyond which the filter substrate material can absorb the heat, resulting in melting or other damage to the filter. Less damaging uncontrolled or spontaneous regeneration of the filter can also take place at noxidation temperatures, i.e., when the filter temperature falls between about 250 C and 400 C. Such uncontrolled regeneration generally does not result in runaway temperatures, but can result in only partial regeneration of the soot on the filter. Partial regeneration can also occur when a controlled regeneration cannot continue because of a drop in temperature, a drop in exhaust gas flow rate, non-uniform temperatures radially and/or axially along the interior of the DPF, or the like. Partial regeneration and other factors can result in non-uniformity of soot distribution across the filter, resulting in soot load estimation inaccuracies and other problems.

The temperature of the particulate filter is dependent upon the temperature of the exhaust gas entering the particulate filter. Accordingly, the temperature of the exhaust must be carefully managed to ensure that a desired particulate filter inlet exhaust gas temperature is accurately and efficiently reached and maintained for a desired duration to achieve a controlled regeneration event that produces desired results. Conventional systems use various strategies for managing the particulate filter inlet exhaust gas temperature. For example, some systems use a combination of internal and external fuel dosing strategies. Each strategy is designed to produce excess UHC in the exhaust gas stream prior to entering the oxidation catalyst (e.g., diesel oxidation catalyst (DOC)). The oxidation catalyst induces an exothermic oxidation reaction of the UHC, which causes the temperature of the exhaust to increase. The amount of UHC added to the exhaust gas is selected to achieve the desired temperature increase or target controlled regeneration temperature.

The oxidation catalyst is also configured to convert NO in the exhaust gas to the more useful compound NO₂. As discussed above, NO₂ is required for noxidation of the DPF. Accordingly, the ability of the oxidation catalyst to convert NO to NO₂ is directly related to the ability of the DPF to be regenerated via noxidation.

SUMMARY

The subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available filter regeneration control systems. Accordingly, the subject matter of the present application has been developed to provide apparatus, systems, and methods for selectively and synergistically modulation between active and passive regeneration processes that overcomes at least some shortcomings of the prior art regeneration control strategies.

For example, according to one embodiment, an apparatus for controlling the regeneration of a particulate filter of an exhaust aftertreatment system of an internal combustion engine system includes an operating conditions module that is configured to monitor at least one condition of the internal combustion engine system (e.g., the condition of a particulate filter of the exhaust aftertreatment system). The apparatus also includes a regeneration module that is configured to trigger a regeneration event if the at least one condition of the engine or exhaust aftertreatment system meets a threshold. Further, the apparatus includes a thermal management module that is configured to operate the internal combustion engine system in a thermal management mode for a first time period while a regeneration event is triggered by the regeneration module. The thermal management mode may include changing the operation of the engine, internal post-injection dosing of fuel into the combustion chambers, external dosing of fuel into the exhaust gas, burners, electrical heaters, and/or other techniques. Also, the apparatus includes a high NO_(x) module configured to operate the internal combustion engine system in a high NO_(x) mode for a second time period following the first time period while the regeneration event is triggered by the regeneration module.

In some implementations of the apparatus, operation of the engine system in the thermal management mode results in oxidation regeneration of the particulate filter, and operation of the engine system in the high NO_(x) mode results in noxidation regeneration of the particulate filter. The length of the first time period can be dependent on a temperature of the exhaust gas exiting an oxidation catalyst upstream of the particulate filter. In one implementation, the first time period ends when a temperature of the exhaust gas exiting an oxidation catalyst upstream of the particulate filter exceeds an oxidation catalyst outlet temperature threshold for a predetermined amount of time. The oxidation catalyst outlet temperature threshold can be the difference between an oxidation catalyst outlet target temperature and an allowable temperature variation. In one implementation, the first time period ends when a temperature of the exhaust gas exiting the particulate filter exceeds a particulate filter outlet temperature threshold. The predetermined amount of time can be less than 50% of the amount of time necessary to substantially completely regenerate the particulate filter via noxidation regeneration. The second time period can be between approximately 90% and 98% longer than the first time period. The predetermined amount of time in the first time period can be set arbitrarily; however, the second time period, with no hydrocarbon dosing across the DOC, can be dependent on how quickly the temperature drops below the range where noxidation is not effective.

According to some implementations of the apparatus, the at least one condition of the internal combustion engine system an amount of particulate matter accumulated on the particulate filter and the threshold includes a maximum allowable amount of particulate matter accumulated on the particulate filter.

In certain implementations, the second time period begins after the first time period ends, when a temperature of exhaust gas exiting an oxidation catalyst upstream of the particulate filter is greater than a minimum temperature associated with a NO₂-to-NO_(x) ratio of at least a threshold ratio, and when a NO_(x) reduction efficiency of a selective catalytic reduction (SCR) catalyst is greater than a minimum efficiency threshold. In yet some implementations, the second time period begins after the first time period ends, when an estimate of the NO₂ flux exiting an oxidation catalyst upstream of the particulate filter exceeds an oxidation catalyst outlet NO₂ flux threshold, and when a NO_(x) reduction efficiency of a selective catalytic reduction (SCR) catalyst is greater than a minimum efficiency threshold. According to one implementation, the second time period ends when a temperature of a bed of an oxidation catalyst upstream of the particulate filter drops below a minimum oxidation catalyst bed temperature. The minimum oxidation catalyst bed temperature can be the bed temperature at which a predetermined minimum particulate matter burn rate from the particulate matter filter is achievable. In view of one implementation, the second time period ends when a temperature of the exhaust gas entering an oxidation catalyst upstream of the particulate filter is within a predetermined oxidation catalyst inlet exhaust temperature range, a flow rate of exhaust gas through the particulate filter is within a predetermined exhaust flow rate range, and a temperature of a bed of the particulate filter is within a predetermined particulate filter bed temperature range.

According to some implementations, the thermal management module is configured to operate the internal combustion engine system in the thermal management mode for a third time period following the second time period while the regeneration event is triggered by the regeneration module. In one implementation, the triggered regeneration event is untriggered when an amount of particulate matter accumulated on the particulate filter is less than a minimum particulate matter accumulation threshold. In the same, or alternative, implementation, the triggered regeneration event is untriggered when the regeneration event has been triggered for more than a predetermined time threshold.

In one implementation, the high NO_(x) module is further configured to operate the internal combustion engine system in the high NO_(x) mode for a third time period separate from the first and second time periods while a regeneration event is not triggered by the regeneration module.

According to another embodiment, a method for controlling the regeneration of a particulate filter of an internal combustion engine system includes triggering a regeneration of the particulate filter and operating the internal combustion engine system in a thermal management mode if a regeneration of the particulate filter has been triggered and while an at least one first operating condition has not met an at least one first threshold. The method further includes switching operation of the internal combustion engine system from the thermal management mode to a high NO_(x) mode if the regeneration of the particulate filter remains triggered and when the at least one first operating condition meets the at least one first threshold. Additionally, the method includes operating the internal combustion engine system in the high NO_(x) mode while an at least one second operating condition has not met an at least one second threshold. The method also includes ceasing operation of the internal combustion engine system in the high NO_(x) mode when the at least one second operating condition meets the at least one second threshold. In some implementations, the method further includes switching operation of the internal combustion engine system from the high NO_(x) mode back to the thermal management mode after ceasing operation of the internal combustion system in the high NO_(x) mode and when at least one third operation condition has met a third threshold.

In another embodiment, an internal combustion engine system having an internal combustion engine includes an oxidation catalyst in exhaust receiving communication with the internal combustion engine and a particulate filter downstream from the oxidation catalyst, the particulate filter being in exhaust receiving communication with the oxidation catalyst. The system also includes a controller that includes a regeneration module that is configured to initiate a regeneration event on a particulate filter, a thermal management module that is configured to control the regeneration event according to a thermal management mode, and a high NO_(x) module that is configured to control the regeneration event according to a high NO_(x) mode. The controller also includes a switch module that is configured to monitor operating conditions of the internal combustion engine system during the regeneration event and to selectively switch between first and second regeneration states during the regeneration event. The first regeneration state includes enablement of the thermal management module and disablement of the high NO_(x) module. The second regeneration state includes disablement of the thermal management module and enablement of the high NO_(x) module. In some implementations of the system, the switch module switches from the first regeneration state to the second regeneration state when excess oxidation catalyst out NO₂ will not result in excess tailpipe out NO_(x).

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the subject matter of the present disclosure should be or are in any single embodiment. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.

The described features, structures, advantages, and/or characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more embodiments and/or implementations. In the following description, numerous specific details are provided to impart a thorough understanding of embodiments of the subject matter of the present disclosure. One skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced without one or more of the specific features, details, components, materials, and/or methods of a particular embodiment or implementation. In other instances, additional features and advantages may be recognized in certain embodiments and/or implementations that may not be present in all embodiments or implementations. Further, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the subject matter of the present disclosure. The features and advantages of the subject matter of the present disclosure will become more fully apparent from the following description and appended claims, or may be learned by the practice of the subject matter as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the subject matter and are not therefore to be considered to be limiting of its scope, the subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which:

FIG. 1 is a schematic diagram of an engine system having an oxidation catalyst and a particulate filter according to one embodiment;

FIG. 2 is a schematic diagram of a controller of the engine system according to one embodiment;

FIG. 3 is a schematic diagram of a controller of the engine system according to another embodiment;

FIG. 4 is a schematic diagram of a thermal management module of the controller of FIG. 2;

FIG. 5 is a schematic diagram of a high NO_(x) module of the controller of FIG. 2;

FIG. 6 is a schematic diagram of a switch module of the controller of FIG. 2; and

FIG. 7 is a flow chart diagram of method for controlling a regeneration event on a particulate filter of an internal combustion engine system according to one embodiment.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

As discussed above, the present disclosure relates to controlling a regeneration event on a particulate matter filter in an engine system. A filter regeneration event occurs when the exhaust gas temperature is sufficiently increased and amounts of soot are oxidized on the particulate filter. Two types of particulate matter oxidation can occur. First, oxidation can occur in the presence of NO₂ at modest filter temperatures (e.g., between about 250° C. and about 400° C.) achieved by modest exhaust gas temperatures to consume modest amounts of particulate matter. Filter regeneration where oxidation occurs in the presence of NO₂ is hereinafter referred to as “noxidation regeneration.” Second, oxidation can occur in the presence of oxygen at high filter temperatures (e.g., greater than about 400° C.) achieved by high exhaust gas temperatures to consume large amounts of particulate matter. Filter regeneration where oxidation occurs in the presence of oxygen is hereinafter referred to as “oxidation regeneration.” In the same regeneration event of the present disclosure, both noxidation and oxidation regeneration can occur.

Unfortunately, the engine exhaust gas temperatures necessary to initiate and maintain oxidation regeneration are often sufficiently high to cause safety concerns, premature component failures, and abnormally high wear on the engine. Moreover, the excess unburned hydrocarbons (UHC) fuel injected into the exhaust gas necessary to increase the temperature reduces the fuel efficiency of the engine system. Accordingly, utilizing noxidation regeneration at lower exhaust gas temperatures to reduce the accumulation of particulate matter on a filter is desirable. However, noxidation regeneration removes particulate matter on the filter at a lower rate at the lower temperatures typically associated with conventional noxidation regeneration. To remove particulate matter at a higher rate using noxidation regeneration, the temperature of the exhaust gas and filter must be elevated above the modest exhaust gas temperatures commonly associated with noxidation regeneration. For example, some particulate filters are catalyzed, which may allow a single NO₂ molecule to be used multiple times to oxidize particulate matter on the filter. Accordingly, some catalyzed particulate filters may favor higher temperatures for noxidation regeneration even if the amount of NO₂ entering the particulate filter is relatively lower at the higher temperatures.

As discussed above, to increase the exhaust gas temperatures, conventional systems inject UHC, either internally or externally, into the exhaust gas upstream of the DOC. But, the ability of the DOC to convert NO_(x) to NO₂, which is necessary for noxidation regeneration to occur, is inversely proportional to amount of UHC in the exhaust gas. In other words, as the amount of UHC in the exhaust gas increases, the ability of the DOC to convert NO_(x) to NO₂, and the noxidation regeneration effectiveness, correspondingly decreases. Therefore, under current practices, it is severely difficult, if not impossible, to conduct noxidation regeneration at high exhaust temperatures because increasing exhaust temperatures requires UHC, which significantly dilutes the ability of the DOC to generate the NO₂ required for such noxidation. Put another way, current systems fail to adequately utilize noxidation regeneration because NO₂ concentration in exhaust flow is limited by DOC conversion efficiency at lower temperatures, due to UHC inhibition when UHC is used to raise the exhaust temperature, and by a thermodynamic equilibrium at higher temperatures (e.g., greater than about 450° C.).

According to some embodiments, the engine system of the present disclosure provides a regeneration control strategy that truncates oxidation regeneration at high temperatures, and provides for prolonged noxidation regeneration at higher temperatures, which may result in improved fuel efficiency (e.g., excess UHC injections reduced), increased longevity of system components (e.g., time exposed to high oxidation regeneration temperatures is reduced), and lower costs (e.g., fewer precious metals on catalysts of system would be required). Accordingly, the current disclosure can be defined to introduce a synergetic active-passive (SAP) regeneration strategy. Essentially, the engine system facilitates a raise in the temperature of the particulate filter while maintaining a reasonable NO₂ conversion by the DOC. FIG. 1 depicts one exemplary embodiment of an internal combustion engine system, such as a diesel engine system 100, in accordance with the present disclosure. As illustrated, the engine system 100 includes an internal combustion engine 110, a controller 130, fuel injectors 135, exhaust after-treatment system 160, and fuel tank 180. The internal combustion engine 110 can be a diesel-powered engine and the fuel tank 180 can store and provide diesel fuel to the engine.

The engine system 100 may further include an air inlet 112, intake manifold 114, exhaust manifold 116, turbocharger turbine 118, turbocharger compressor 120, and various sensors, such as temperature sensors 124, pressure sensors 126, and exhaust characteristic sensors 165. In one embodiment, the air inlet 112 is vented to the atmosphere, enabling air to enter the engine system 100. The air inlet 112 may be connected to an inlet of the intake manifold 114. The intake manifold 114 includes an outlet operatively coupled to the combustion chambers 111 of the engine 110. Within the engine 110, compressed air from the atmosphere is combined with fuel to power the engine 110, which comprises operation of the engine 110. The fuel comes from the fuel tank 180 through a fuel delivery system including, in one embodiment, a fuel pump and common rail 131 to the fuel injectors 135, which injects fuel into the combustion chambers 111 of the engine 110. Fuel injection timing is controlled by the controller 130. Combustion of the fuel produces exhaust gas that is operatively vented to the exhaust manifold 116. From the exhaust manifold 116, at least a portion of the exhaust gas may be used to power a turbocharger turbine 118 before entering the exhaust after-treatment system 160. The turbine 118 may drive the turbocharger compressor 120, which compresses engine intake air before directing it to the intake manifold 114.

Some amount of the exhaust gas may bypass the turbine 118 and be re-circulated to the engine 110 via an EGR line 152 according to a proportion set by the controller 130. In one embodiment, an EGR valve 154 is actuated by the controller 130 to divert an amount of exhaust gas corresponding to the set proportion through the EGR line 152.

The portion of exhaust gas not re-circulated to the engine 110 via the EGR line 152 is destined for expulsion from the system 100 into the atmosphere. Prior to being vented into the atmosphere, the exhaust gas passing through the turbine 118 is directed through the exhaust after-treatment system 160 to reduce harmful emissions in the exhaust gas. The exhaust after-treatment system 160 shown in FIG. 1 includes an oxidation catalyst 140, a particulate filter 150, and a selective catalytic reduction (SCR) catalyst 170. The exhaust gas initially passes through the oxidation catalyst 140, which reduces specific pollutants is the exhaust gas as discussed above and, when regeneration of the filter is triggered, elevates the temperature of the exhaust gas to a desired filter inlet exhaust gas temperature prior to entering the filter 150. Regeneration of the filter is triggered and controlled by operation of the controller 130. Then the exhaust gas passes through the particulate filter 150, which filters particulate matter out of the exhaust stream. After passing through the particulate filter 150, the exhaust gas passes through the SCR catalyst 170, which reduces NO_(x) in the exhaust gas into less harmful constituents in the presence of a reductant, such as urea, which reduces to ammonia, injected into the exhaust gas via a reductant injector 172.

The various sensors, such as temperature sensors 124, pressure sensors 126, exhaust characteristic sensors 165, and the like, may be strategically positioned throughout the engine system 100 and may be in communication with the controller 130, which ascertains and monitors operating conditions of the engine based at least partially on the input received from the sensors. In one embodiment, each exhaust characteristic sensor 165 represents one or more sensors each configured to detect a particular characteristic of the exhaust gas. For example, the exhaust characteristic sensor 165 may include a NO_(x) sensor configured to detect the concentration of NO_(x) in the exhaust gas stream. The exhaust characteristic sensor 165 may also include an exhaust flow rate sensor configured to detect the flow rate of exhaust through the after-treatment system 160. Other sensors may be used to determine other operating conditions of the engine system 100 directly via detection and measurements or indirectly via calculations performed by or tables stored on the controller. In other words, each sensor of the system 100 may be one or more of a physical sensor or virtual sensor as is known in the art. Other operating conditions that can be determined by the sensors include, but are not limited to, fraction of exhaust gas recirculation, injection timing, fuel rate, engine speed, engine load, the timing at which fuel injection timing is advanced or retarded (SOI, or start of injection), time passed, fraction of exhaust gas recirculation, driving conditions, whether and when regenerations have occurred and the rate such regenerations have removed particulate matter, exhaust flow rate, the amount of O₂ and NO₂ in the exhaust, filter temperature, exhaust gas pressure, filter particulate load amount and uniformity, emissions reduction efficiency of the exhaust after-treatment components, etc.

FIG. 2 depicts a control system 200 according to one representative embodiment. The control system 200 comprises the controller 130, one or more sensors 290 (e.g., sensors 124, 126, 165), one or more engine system actuators 295, and one or more fuel injectors (e.g., injectors 135, 137). Fuel injector 137 is an external fuel injector configured to inject fuel (e.g., UHC) directly into the exhaust gas prior to the gas passing through the oxidation catalyst 140.

The controller 130 controls the operation of the engine system 100 and associated sub-systems, such as the engine 110 and exhaust gas after-treatment system 160. The controller 130 is depicted in FIGS. 1 and 2 as a single physical unit, but can include two or more physically separated units or components in some embodiments if desired. Generally, the controller 130 receives multiple inputs, processes the inputs, and transmits multiple outputs. The multiple inputs may include sensed measurements from the sensors and various user inputs. The inputs are processed by the controller 130 using various algorithms, stored data, and other inputs to update the stored data and/or generate output values. The generated output values and/or commands are transmitted to other components of the controller and/or to one or more elements of the engine system 100 to control the system to achieve desired results, and more specifically, achieve desired exhaust gas emissions.

The controller 130 includes various modules for controlling the operation of the engine system 100. For example, in the illustrated embodiment, the controller 130 includes an input module 240, a conditions module 250, a regeneration module 260, an output module 270, a thermal management module 275, a high NO_(x) module 280, and a switch module 285. As is known in the art, the controller 130 and components may comprise processor, memory, and interface modules that may be fabricated of semiconductor gates on one or more semiconductor substrates. Each semiconductor substrate may be packaged in one or more semiconductor devices mounted on circuit cards. Connections between the modules may be through semiconductor metal layers, substrate-to-substrate wiring, or circuit card traces or wires connecting the semiconductor devices.

As mentioned above, the sensors 290 of the system 100 are configured to determine, whether directly or indirectly, a plurality of conditions within the engine system 100, including temperature, pressure, NO_(x) concentration, exhaust gas flow rate, etc. The engine system actuators 295 are any of various components of the system 100 that when actuated affect the operating conditions of the system. For example, the actuators 295 may include an exhaust throttle, intake throttle, reductant injector, EGR valves, fuel injectors, etc. The input module 240 is configured to receive and input the conditions sensed by the sensors 290 and provide corresponding inputs to the regeneration module 260, high NO_(x) module 280, and switch module 285. The conditions module 250 is configured to gather information regarding current conditions of the engine system 100, based on the conditions sensed by the sensors 290 and/or other inputs including commands issued to system components by the controller 130. The output module 270 is configured to direct the engine system actuators 295 and/or fuel injectors 135, 137 (e.g., via commands) according to regeneration instructions generated by the regeneration module 260, thermal management module 275, high NO_(x) module 280, and switch module 285.

FIG. 3 is a schematic block diagram illustrating another embodiment of the control system 200 of FIG. 2. The controller 130 is depicted as comprising a processor module 302, memory module 304, and interface module 306. The processor module 302, memory module 304, and interface module 306 may be fabricated of semiconductor gates on one or more semiconductor substrates. Each semiconductor substrate may be packaged in one or more semiconductor devices mounted on circuit cards. Connections between the processor module 302, the memory module 304, and the interface module 306 may be through semiconductor metal layers, substrate to substrate wiring, or circuit card traces or wires connecting the semiconductor devices.

The memory module 304 stores software instructions and data comprising one or more software processes. The processor module 302 executes the software processes as is known to those skilled in the art. In one embodiment, the processor module 302 executes one or more software processes carried out by the conditions module 250, regeneration module 260, thermal management module 275, high NO_(x) module 280, and switch module 285 of FIG. 2.

The processor module 302 may communicate with and control external devices and sensors, such as the sensors 290, the actuators 295, and the fuel injectors 135, 137 of FIG. 2 through the interface module 306. For example, the sensors 290 may include a pressure sensor 126 (see, e.g., FIG. 1) that communicates an analog signal representing a pressure value to the interface module 306. The interface module 306 may periodically convert the analog signal to a digital value and communicate the digital value to the processor module 302. The interface module 306 may also receive one or more digital signals through a dedicated digital interface, a serial digital bus communicating a plurality of digital values, or the like. For example, the sensors 290 may include a temperature sensor 124 (see, e.g., FIG. 1) that communicates a digital temperature value to the interface module 306. The interface module 306 may periodically communicate the digital temperature value to the processor module 302. In one embodiment, the interface module 306 executes one or more communication processes carried out by the input module 240 and output module 270 of FIG. 2.

The processor module 302 may store digital values such as the pressure value and the temperature value in the memory module 304. In addition, the processor module 302 may employ the digital values in one or more calculations including calculations carried out by the modules of the controller 130. Although the above description was limited to a pressure sensor and temperature sensor, the interface module 306 can interface with any of the various sensors of the system 100 to receive detected values for any of various sensed characteristics of the system.

Referring back to FIG. 1, particulate matter produced by the engine 110 comprises ash and soot. The engine 110 will produce soot and ash at a rate that will vary according to the type of engine, such as, for example, an 11-liter or 15-liter diesel engine. Additionally, the rate of particulate production will vary according to engine operating conditions such as fuel rate, EGR fraction, and SOI timing. Other factors may also bear on the particulate production rate, some depending heavily on the engine platform being considered, with others closer to being platform-independent.

Generally, the accumulation of particulate matter on the particulate filter (e.g., filter 150) must be removed periodically to ensure that the amount of particulate matter accumulated on the filter does not reach dangerous or undesirable levels. Removal of the accumulated particulate matter is performed during a regeneration event to effectively regenerate the filter. The control system of the present disclosure is configured to initiate and control a regeneration event on a particulate matter filter. Generally, the regeneration event controlled by the control system combines active regeneration (i.e., oxidation regeneration) and passive regeneration (i.e., noxidation regeneration) by modulating the bed temperatures of the oxidation catalyst and filter between high and low temperature levels. Also, in general terms, according to one embodiment, the regeneration control strategy executed by the controller 130 includes artificially driving the temperature of the filter bed up to a temperature high enough for oxidation and holding the temperature steady for a small amount of time (e.g., just long enough to stabilize the temperature), then allowing the temperature of the filter bed to naturally fall downwardly while artificially generating excess NO₂ in the exhaust gas to facilitate noxidation regeneration of the filter as the temperature falls. Then, once the temperature falls below a certain low temperature threshold, driving the temperature back up to the oxidation regeneration temperature and repeating the same pattern for as long as regeneration of the filter is necessary.

Regeneration of the particulate filter is initiated and at least partially controlled by the regeneration module 260. Basically, the regeneration module 260 is configured to generate a regeneration command (e.g., regeneration instructions) representing a request to initiate a regeneration event on the particulate filter 150. In other words, based on input from the conditions module 250, the regeneration module 260 triggers a regeneration event when operating conditions indicate regeneration of the particulate filter 150 is necessary.

In one embodiment, the regeneration module 260 triggers a regeneration event based exclusively or partially on an estimate of the amount of particulate matter accumulated on the particulate filter 150. The estimate can be based on a sensed pressure differential across the particulate filter 150 using pressure sensors 126 positioned upstream and downstream of the filter as shown in FIG. 1. In certain implementations, a regeneration event is triggered by the regeneration module 260 when an estimated accumulation of particulate matter on the filter exceeds an upper threshold load. In some implementations, the estimate of the amount of particulate matter accumulated on the filter may be determined based on another method as is known in the art.

In another embodiment, the regeneration module 260 triggers a regeneration event based on whether an operating period of the engine has exceeded some time threshold. For example, if the engine has operated for a predetermined amount of time, an assumption is made concerning the amount of accumulation on the particulate filter. This assumption made be based on a model predicting the amount of accumulation that has likely accumulated on the filter in view of various factors, such as the type of engine, the type of driving experience by a vehicle in which the engine is housed, and the like. In one implementation, the regeneration module 260 automatically triggers the regeneration event once an operating time threshold has been met regardless of the actual amount of accumulation on the filter. The time period may be adjusted or determined exclusively of or dependent upon a real-time estimate of the accumulation on the filter as discussed above.

Additionally, or alternatively, in some embodiments, the regeneration command is issued by the regeneration module 260 to initiate a regeneration event based on any of various other parameters, such as, for example, operating conditions of the engine other than a pressure differential across the filter, the availability of future regeneration opportunities, the operating trends of the engine, etc.

After the regeneration module 260 triggers a regeneration event, the thermal management module 275 is operable to initiate an oxidation regeneration of the particulate filter. The thermal management module 275 includes a temperature target module 310 that determines a desired filter inlet exhaust gas temperature 360 (i.e., desired oxidation catalyst or DOC outlet exhaust gas temperature) based on the engine operating conditions 330. Generally, the desired filter inlet exhaust gas temperature corresponds with a desired temperature of the filter bed for initiating oxidation regeneration of the filter. The desired filter inlet exhaust gas temperature 360 is communicated to an engine controls module 315 and a fuel injection strategy module 320.

The engine controls module 315 is configured to generate engine one or more temperature controls commands 345 to control non-fuel related operations of the engine to produce or provide operating conditions conducive to producing the desired filter inlet exhaust gas temperature 460. For example, the particulate filter inlet exhaust gas temperature can be manipulated through one or more air handling strategies. The air handling strategies may include managing an air intake throttle to regulate the air-to-fuel ratio. More specifically, the engine temperature controls commands 345 may include commands transmitted to an intake throttle to artificially lower the air-to-fuel ratios, e.g., richer air/fuel mixtures, to produce higher engine outlet exhaust gas temperatures, and thus higher particulate filter inlet exhaust gas temperatures. In embodiments in which an oxidation catalyst is not positioned in the exhaust gas stream between the exhaust manifold 116 and the particulate filter 150, the engine controls module 315 commands the engine to produce an engine outlet exhaust gas temperature equal to the desired filter inlet exhaust gas temperature.

However, in some embodiments, it may be undesirable or difficult to achieve engine outlet exhaust gas temperatures that are equal to the desired filter inlet exhaust gas temperature 360. Accordingly, an oxidation catalyst 140 can be utilized to replace or supplement the artificial increase in engine outlet exhaust temperature in order to achieve the desired filter inlet exhaust gas temperature 360.

In some implementations, the increase in the desired filter inlet exhaust gas temperature 360 is generated nearly exclusively according to fuel dosing strategies configured to utilize the functionality of the oxidation catalyst 140 to increase the exhaust gas temperature as discussed above. Fuel dosing strategies include internal fuel dosing strategies and external fuel dosing strategies.

Internal fuel dosing strategies include injecting additional fuel into the compression cylinders. Such in-cylinder injections make up a multiple-injection event that includes pre-injections or fuel injections occurring before a main fuel injection and post-injections or fuel injection occurring after a main fuel injection. Generally, post-injections include heat post-injections and non-heat post-injections. Heat post-injections are injections that participate along with the main fuel injection in the combustion event within the cylinder and occur relatively soon after the main fuel injection. Non-heat post injections are injections that occur later in the expansion stroke compared to the heat post-injections and do not participate in the combustion event within the cylinder.

In one embodiment associated with an internal fuel dosing strategy, based at least partially on the desired filter inlet exhaust gas temperature 360 received from the temperature target module 310 and the operating conditions 330 of the engine, the fuel injection strategy module 320 generates one or more fuel injection commands 350 to the fuel injectors. The fuel injectors 135 respond to the fuel injection command 350 by injecting fuel into the compression chambers 111 according to the fuel injection command. The fuel injection command includes instructions for performing a multiple-injection event. The instructions may include relative timing of a plurality of fuel injections and the quantity or dosage of fuel injected in each of the plurality of fuel injections. The excess fuel injected into the chambers 111 via the multiple-injection event is transferred to the exhaust gas emitted from the engine 110 or exhaust manifold 116 in the form of UHC. As discussed above, the excess UHC is oxidized by the oxidation catalyst 140, which results in an increase in the exhaust gas temperature. In certain implementations, the commanded amount of excess UHC added to the exhaust gas via the internal fuel dosing strategy corresponds with an exhaust temperature increase (via oxidation of the UHC in the oxidation catalyst 140) necessary to achieve the desired filter inlet exhaust gas temperature 360.

In addition to, or separate from, internal fuel dosing strategies, external fuel dosing strategies can be used to add excess UHC to the exhaust gas for raising the temperature of the exhaust gas. External fuel dosing strategies include injecting additional fuel directly into the exhaust gas stream via one or more fuel injectors (e.g., fuel injector 137) located downstream of an engine exhaust outlet and upstream of the oxidation catalyst 140. According to some implementations, the fuel injection strategy module 320 is configured to generate a fuel injection command 350 to the fuel injector 137 to inject a desired amount of fuel into the exhaust gas stream. As with internal fuel dosing strategies, the commanded amount of excess UHC added to the exhaust gas via the external fuel dosing strategy may correspond with an exhaust temperature increase necessary to achieve the desired filter inlet exhaust gas temperature 360. Alternatively, the fuel injection strategy module 320 may be configured to utilize both internal and external fuel injection strategies to achieve the desired filter inlet exhaust gas temperature 360 by generating fuel injection commands 450 to the injectors 135 and injector 137 to collectively add the desired amount of excess UHC to the exhaust gas.

In some implementations, some increase in the engine outlet exhaust temperature, in addition to the increase affected by fueling strategies in conjunction with the oxidation catalyst 140, may be necessary to achieve the desired filter inlet exhaust gas temperature 360. In such implementations, the engine controls module 315 and fuel injection strategy module 320 communicate with each other as indicated in FIG. 4 to generate engine temperature controls commands 345 and fuel injection commands 350 that cooperatively increase the exhaust gas temperature via non-fuel dosing strategies and fuel dosing strategies, respectively. Accordingly, in some embodiments where the engine system 100 includes an oxidation catalyst 140, the thermal management module 275 compensates for any temperature changes in the exhaust due to operation of the oxidation catalyst component by setting the desired engine outlet exhaust gas temperature such that the exhaust exiting the oxidation catalyst is approximately equal to the desired filter inlet exhaust gas temperature. In one implementation, for example, the thermal management module 275 first utilizes non-fuel dosing strategies to increase the temperature of the exhaust exiting the engine and entering the oxidation catalyst 140 to a temperature above an UHC light-off temperature, which can be a predetermined temperature necessary for exothermic UHC oxidation to occur. Once the exhaust gas reaches the UHC light-off temperature, then the thermal management module 275 initiates fuel dosing strategies to further increase the temperature of the exhaust gas to achieve the desired or target filter inlet exhaust gas temperature 360.

Referring to FIG. 5, the high NO_(x) module 280 is configured generally to artificially increase the amount of NO_(x) in the exhaust gas stream generated by the engine 110. In one implementation, the high NO_(x) module 280 artificially increases the amount of NO_(x) in the exhaust gas stream in anticipation of noxidation regeneration of the filter 150. For example, while regeneration of the filter 150 is triggered (e.g., the estimated accumulation of particulate on the filter is above a threshold or the amount of time since initiation of a regeneration event is below a threshold), and if other operating conditions are met, the high NO_(x) module 280 issues one or more engine NO_(x) control commands 405 to operate the engine 110 in a high NO_(x) mode. The other operating conditions are certain operating conditions that ensure running the engine in the high NO_(x) mode will result in more particulate accumulation being removed via noxidation regeneration without significantly increased levels of NO_(x) exiting the system into the atmosphere. Accordingly, in some implementations, operating the engine in a high NO_(x) mode corresponds with regeneration of the particulate filter according to a noxidation regeneration process.

However, in other implementations, operating the engine in a high NO_(x) mode does not correspond with accelerated noxidation regeneration of the engine, but can correspond with operating conditions that are able to handle high levels of NO_(x) in the exhaust gas without failing to meet exhaust emissions requirements. As discussed herein, operation of the engine system in the high NO_(x) mode provides many benefits (e.g., increased fuel economy) in addition to accelerated noxidation regeneration. Accordingly, if the conditions of the engine system are such that artificially higher levels of NO_(x) in the exhaust stream can be sufficiently reduced by NO_(x) reduction technologies used in exhaust aftertreatment systems, such as SCR systems, the high NO_(x) module 280 initiates operation in the high NO_(x) mode to achieve the benefits that operation in the high NO_(x) mode can provide. For example, even when a regeneration event is not triggered, the high NO_(x) module 280 may be triggered to operate the engine system in the high NO_(x) mode when one or more operating conditions meets prescribed thresholds. In one implementation, the high NO_(x) module 280 is triggered to operate the engine system in the high NO_(x) mode, among other possible conditions, when an estimated amount of soot collected in the DPF is above a threshold, when the exhaust aftertreatment system temperature is above a threshold, and/or when operating conditions are conducive for very high NO_(x) reduction efficiency by the SCR system.

In some embodiments, operation in the high NO_(x) mode produces substantially higher amounts of NO_(x) compared to the amount of NO_(x) produced under the same operating conditions during normal engine operation. In one particular implementation, the amount of NO_(x) produced during operation in the high NO_(x) mode is at least about 20% higher than the amount of NO_(x) produced during normal engine operation under the same or similar operating conditions. In yet some implementations, the amount of NO_(x) produced during operation in the high NO_(x) mode is up to about 50% higher, and in some instances about 100% or more higher, than the amount of NO_(x) produced during normal engine operation under the same or similar operating conditions.

In certain implementations, the engine NO_(x) control command(s) 405 include commands for actuating various engine actuators to increase (e.g., optimize) fuel economy, increase the concentration of NO_(x) in exhaust gas exiting the engine 110, and maintain for an extended time the temperature of the exhaust gas exiting the engine at elevated temperatures within the noxidation regeneration range. In one particular implementation, the engine NO_(x) control commands 405 include commands to lower the amount of fuel injected into the combustion chambers of the engine (e.g., create extra lean conditions within the chambers), increase the amount of air in the combustion chambers (e.g., via actuation of intake throttle or EGR valve), and adjust the fuel injection timing.

Because of stringent exhaust emission regulations, fuel economy is often hampered. In other words, in some systems, in order to achieve regulated exhaust emissions (e.g., low NO_(x) levels), the engine must be operated in a mode associated with less-than-desirable fuel economy. However, fuel economy can be improved when the engine is operating in the high NO_(x) mode because limitations imposed, due to lower engine out NO_(x) targets constraints, on the fuel consumption are removed. Basically, the high NO_(x) mode is operated when certain operation conditions associated with SCR catalyst performance are met, such as, for example, the exhaust temperature and space velocity are in the high performance range of the SCR catalyst. The fuel consumption reduced in this manner during operation in the high NO_(x) mode, and the removal of soot without the use of UHC helps improve the fuel consumed during regeneration events. This benefit is particularly evident when an engine is operated under moderate to highly transient (e.g., stop-and-go and city) driving conditions.

Referring to FIG. 6, the switch module 285 includes an oxidation catalyst condition module 420, a particulate filter condition module 425, an SCR catalyst condition module 430, an exhaust condition module 432, and a logic module 435. Generally, the switch module 285 is configured to switch the regeneration mode between an oxidation regeneration mode and a noxidation regeneration mode during a regeneration event. Based on engine operating conditions 440, the switch module 285 generates a regeneration state command 480 that is transmitted to the thermal management module 275, high NO_(x) module 280, and regeneration module 260. The command 480 includes instructions to either conduct oxidation regeneration (i.e., enable the thermal management module 275 and disable the high NO_(x) module 280), conduct noxidation regeneration (i.e., disable the thermal management module and enable the high NO_(x) module), or stop an ongoing regeneration event (i.e., disable both the thermal management module and high NO_(x) module). Accordingly, based on the engine operating conditions 440 during a triggered regeneration event, the switch module 285 determines which of an oxidation and noxidation regeneration is appropriate for a given set of operating conditions and, if necessary, switching from operation in one of the oxidation and noxidation regeneration modes to the other of the modes when appropriate.

The oxidation catalyst condition module 420 determines or assesses various operating conditions associated with the oxidation catalyst 140. For example, in one implementation, the engine operating conditions 440 may include input from an oxidation catalyst outlet temperature sensor 124 downstream from the oxidation catalyst 140 and upstream from the particulate filter 150. Based on the oxidation catalyst outlet temperature sensor input, the oxidation catalyst condition module 420 determines an oxidation catalyst outlet exhaust temperature. In another implementation, the engine operating conditions 440 may include additional inputs and the oxidation catalyst condition module 420 may determine a temperature of the bed of the oxidation catalyst 140. In yet other implementations, the engine operating conditions 440 may include input from an oxidation catalyst inlet temperature sensor upstream from the oxidation catalyst 140. Based on the oxidation catalyst inlet temperature sensor input, the oxidation catalyst condition module 420 determines an oxidation catalyst inlet exhaust temperature. In some implementations, the oxidation catalyst inlet exhaust temperature can be measured, determined, or estimated using other techniques, such as through the use of models, virtual sensors, and physical sensors in direct contact with the catalyst. In other implementations, the oxidation catalyst condition module 420 determines the flux of NO₂ exiting the oxidation catalyst 140.

The particulate filter condition module 425 determines or assesses various operating conditions associated with the particulate filter 150. For example, the engine operating conditions 440 may include input from a filter outlet temperature sensor 124 downstream from the particulate filter 150. Based on the filter outlet temperature sensor input, the oxidation catalyst condition module 425 determines an oxidation catalyst outlet exhaust temperature. The engine operating conditions 440 may also include other inputs, such as input from the oxidation catalyst outlet temperature sensor 124 (or filter inlet temperature sensor) and/or other inputs from which the particulate filter condition module 425 determines a temperature of the bed of the particulate filter 150.

The SCR catalyst condition module 430 determines or assesses various operating conditions associated with the SCR catalyst 170. For example, in one implementation, the engine operating conditions 440 may include input from virtual and/or physical sensors. Based on the inputs, the SCR catalyst condition module 430 determines a NO_(x) reduction efficiency of the SCR catalyst 170.

The exhaust condition module 432 of the switch module 285 determines or assesses various operating conditions associated with the exhaust gas in the system 100. For example, in one implementation, the engine operating conditions 440 may include input from virtual or physical sensors that is used to determine the amount of NO_(x) present in the exhaust gas during operation in the high NO_(x) mode and the flow rate of exhaust gas through the after-treatment system 160.

The logic module 435 of the switch module 285 includes logic configured to generate the regeneration state command 480 based on one or more outputs from the oxidation catalyst condition module 420, particulate filter condition module 425, SCR catalyst condition module 430, and exhaust condition module 432. Generally, the logic module 435 stores or calculates one or more threshold values and generates the regeneration state command 480 based on a comparison between the outputs from the modules 420, 425, 430, 432 and the threshold values.

One of the engine operating conditions 440 received by the switch module 285 includes the triggering of a regeneration event by the regeneration module 260. After a regeneration event is triggered, the switch module 285 is enabled to generate a regeneration state command 480 including instructions to enable the thermal management module 275 and disable the high NO_(x) module 280. Once this regeneration state command 480 is received by the thermal management module 275, the thermal management module initiates an oxidation regeneration process as discussed above, and the high NO_(x) module 280 is disabled.

The logic module 435 monitors conditions of the system 100 during the oxidation regeneration process controlled by the thermal management module 275 and initiates a switch to a noxidation regeneration process after a first time period (i.e., the time from initiation of the oxidation regeneration process to a time when the monitored conditions meet certain thresholds). When the thresholds are met and a switch is desired, a new regeneration state command 480 is generated by the logic module 435 with instructions to disable the thermal management module 275 and enable the high NO_(x) module 285. Once the new regeneration state command 480 is received by the high NO_(x) module 285, the high NO_(x) module initiates a noxidation regeneration process as discussed above, and the thermal management module 275 is disabled.

In one implementation, the new regeneration state command 480, which switches regeneration from oxidation to noxidation, is issued if the oxidation catalyst outlet temperature determined by the oxidation catalyst condition module 420 exceeds an oxidation catalyst outlet temperature threshold for a calibrated or predetermined amount of time. The oxidation catalyst outlet temperature threshold can be equal to the difference between a target oxidation catalyst outlet temperature and an allowable temperature variation. Generally, in some implementations, the target oxidation catalyst outlet temperature represents the temperature at which oxidation regeneration begins to occur. The allowable temperature variation can be any of various values sufficiently high to compensate for inconsistencies and variabilities that may be present in the system. In some instances, the allowable temperature variation is no more than about 5-10° C. In yet other implementations, the allowable temperature variation is no more than about 20-30° C. or no more than about 50° C. or higher. The predetermined amount of time is selected to be less than an amount of time necessary to substantially completely regenerate the filter 150 solely via oxidation regeneration. In other words, the predetermined amount of time is selected such that the oxidation regeneration controlled by the thermal management module 275 does not completely regenerate the filter 150, and that substantial amount of particulate accumulation remains on the filter when the predetermined amount of time is met.

In certain implementations, the predetermined amount of time is only long enough to ensure that the artificially driven high temperature of the filter is stabilized, before allow the temperature to drop. In fact, in some implementations, the predetermined amount of time is less than 50% of the amount of time necessary to substantially completely regenerate the filter 150 solely via oxidation regeneration. In other implementations, the predetermined amount of time is between about 2% and about 10% of the amount of time necessary to substantially completely regenerate the filter 150 solely via oxidation regeneration. Accordingly, in certain implementations, during a triggered regeneration event, only between about 2% and about 10% of the removal of particulate matter from the filter 150 is attributable to oxidation regeneration, with about 90% to about 98% being attributable to noxidation regeneration. Although there is not necessarily a linear relationship between the amount of soot burned and the time required to burn the soot, the system and method of the present disclosure can, in certain implementations, be configured to burn the majority of the soot with noxidation regeneration.

In another implementation, the new regeneration state command 480, which switches regeneration from oxidation to noxidation, is issued if the filter outlet temperature determined by the particulate filter condition module 425 exceeds a filter outlet temperature threshold. Filter outlet temperature threshold values can be predetermined and be based on various factors, such as the exhaust flow rate (e.g., higher flow rates allow higher filter outlet temperature threshold values) and the soot load estimate (e.g., lower soot load estimates allow higher filter outlet temperature threshold values). Generally, the filter outlet temperature threshold values are low enough to protect the filter and other components of the system from damage due to excessive heat.

The new regeneration state command 480, which switches regeneration from oxidation to noxidation, can be issued if either the oxidation catalyst outlet temperature exceeds the oxidation catalyst outlet temperature threshold for a calibrated or predetermined amount of time or the filter outlet temperature exceeds a filter outlet temperature threshold. Alternatively, the new regeneration state command 480, which switches regeneration from oxidation to noxidation, can be issued only if the oxidation catalyst outlet temperature exceeds the oxidation catalyst outlet temperature threshold for a calibrated or predetermined amount of time and the filter outlet temperature exceeds a filter outlet temperature threshold.

In some implementations, a new regeneration state command 480 that switches regeneration from oxidation in the thermal management mode to noxidation in the high NO_(x) mode is not issued by the logic module 435 unless operating the engine in the high NO_(x) mode will be beneficial (e.g., result in additional and/or more effective noxidation regeneration of particulate matter from the filter 150). In one implementation, the logic module 435 issues the new regeneration state command 480 and transmits it to the high NO_(x) module 280 to enable the high NO_(x) module when first and second operating conditions are met. Basically, in some embodiments, the controller 130 is configured to control the engine system 100 to quickly raise the temperature of the particulate filter bed to a high temperature conducive for oxidation regeneration and maintain high temperature of the bed for a relatively short period of time compared to prior art oxidation regeneration systems. Then, the controller 130 is configured to control the engine system 100 to produce high levels of NO_(x) while halting artificial inflation of the exhaust temperatures and allowing the exhaust temperatures to drop below the high temperature necessary for oxidation regeneration. Because the level of NO_(x) in the exhaust gas is artificially high, more NO_(x) is converted into NO₂. Moreover, because noxidation regeneration is more effective at higher temperatures if enough NO₂ is present, and more NO₂ is present as a result of operation in the high NO_(x) mode, noxidation regeneration of the filter is more effective than conventional methods.

The first operating condition includes either an oxidation catalyst outlet temperature less than a minimum temperature associated with a NO₂-to-NO_(x) ratio of at least a threshold ratio, or an estimate of the oxidation catalyst outlet NO₂ flux is greater than a predetermined above-normal NO₂ flux. An oxidation catalyst outlet temperature that is less than a minimum temperature associated with a NO₂-to-NO_(x) ratio threshold accounts for the reduction of NO₂ levels at higher temperature due to the thermodynamic equilibrium limitation of the NO₂-to-NO_(x) ratio. The NO₂-to-NO_(x) ratio threshold can be between about 0.1 and about 0.3 in some implementations. In certain implementations, the NO₂-to-NO_(x) ratio threshold is about 0.2. An oxidation catalyst outlet NO₂ flux estimate that is greater than a predetermined above-normal NO₂ flux means that operation in the high NO_(x) mode will likely produce elevated amount of NO_(x) in the exhaust gas to meet or exceed an above-normal NO₂ necessary for efficient noxidation regeneration at elevated temperatures.

The second operating condition is that the product of an estimated amount of NO_(x) in the high NO_(x) mode and the NO_(x) reduction efficiency of the SCR catalyst is less than the maximum amount of tailpipe NO_(x) exiting the system allowed during regeneration. The second operating condition accounts for the possibility that the NO_(x) reduction efficiency of the SCR is not high enough to adequately reduce the excess NO_(x) produced in the high NO_(x) mode to a level below the regulated maximum allowable tailpipe NO_(x) during filter regeneration. To ensure compliance with emission regulations, the logic module 285 will not issue a new regeneration state command 480 that switches regeneration from oxidation to noxidation in the high NO_(x) mode unless this second operating condition has been met.

Although two specific operating conditions are discussed above, in other embodiments fewer or more than the two specific operating conditions can be required, or other operating conditions not specifically mentioned can be required before operation in the high NO_(x) mode is allowed. In some instances, the operating conditions can include, but are not limited to, space velocity constraints, O₂ constraints, fuel-speed or torque-speed constraints represented in one or more predetermined maps that dictate the region or regions where operation in the high NO_(x) mode is allowed.

The logic module 435 monitors conditions of the system 100 during the noxidation regeneration process associated with operation of the engine in the high NO_(x) mode and initiates a switch back to an oxidation regeneration process after a second time period (i.e., the time from initiation of the noxidation regeneration process to a time when the monitored conditions meet certain thresholds). When a switch back to oxidation regeneration is desired, a new regeneration state command 480 is generated with instructions to enable the thermal management module 275 and disable the high NO_(x) module 285. Once the new regeneration state command 480 is received by the high NO_(x) module 285, the high NO_(x) module is disabled and the thermal management module 275 initiates an oxidation regeneration process as discussed above. The new oxidation regeneration process continues for a third time period (i.e., the time from initiation of the second oxidation regeneration process to a time when the monitored conditions meet certain thresholds (e.g., the same thresholds associated with the first time period)).

In one implementation, the new regeneration state command 480, which switches regeneration from noxidation back to oxidation, is issued only if the bed temperature of the oxidation catalyst 140 becomes less than a minimum threshold. The oxidation catalyst bed temperature minimum threshold can be a predetermined threshold associated with a minimum burn rate of particulate matter from the filter 150. For example, in one implementation, the minimum burn rate is about 0.1 g/min, and the oxidation catalyst bed temperature minimum threshold is between about 300° C. and about 320° C. depending on the size and chemical make-up (e.g., catalyzed or non-catalyzed) of the filter.

In addition, or alternatively, to requiring the bed temperature of the oxidation catalyst 140 to be less than a minimum threshold, in one implementation, the new regeneration state command 480, which switches regeneration from noxidation back to oxidation, is issued and communicated to the thermal management module 275 only if the system 100 is operating within a predetermined oxidation catalyst inlet exhaust temperature range, an exhaust flow rate range, and a particulate filter bed temperature range. These operating condition ranges are selected and cooperatively precalibrated according to the optimal general operating environments for regenerating the filter using oxidation regeneration versus noxidation regeneration. In other words, when the monitored operating conditions fall within each of the three ranges, the general operating environment is more conducive to oxidation regeneration than noxidation regeneration, and a switch to oxidation regeneration should be implemented. In contrast, when at least one of the monitored operating conditions falls outside of the respective three ranges, the general operating environment is more conducive to noxidation regeneration than oxidation regeneration, and the noxidation regeneration process should be maintained. Accordingly, the logic module 435 issues a new regeneration state command 480 to switch from noxidation regeneration to oxidation regeneration when the general operating environment meets the threshold ranges, and does not issue a new regeneration state command 480 when the threshold ranges are not met. Although the operating condition ranges are associated with the oxidation catalyst inlet exhaust temperature, exhaust flow rate, and the particulate filter bed temperature, fewer or more than these three operating condition ranges can be used to determine the optimal environments for oxidation and noxidation regeneration, respectively.

In some embodiments, even if the monitored burn rate and/or general operating environment suggest a switch from the noxidation regeneration state (high NO_(x) mode) back to an oxidation regeneration state, the logic module 435 will issue a new regeneration state command 480 that stops the regeneration event all together if: (1) the particulate matter filter is sufficiently regenerated; or (2) regeneration of the particulate filter has been triggered for greater than a time threshold (e.g., about 60 minutes in one implementation).

In yet some embodiments, if the monitored burn rate is below a minimum threshold, and continues to remain there for a threshold time, then the logic module 435 will issue a new regeneration state command 480 with instructions to end the high NO_(x) mode (e.g., noxidation regeneration) and reinitiate the oxidation mode. Essentially, if this condition is met, the new regeneration state command 480 includes instructions to disable the high NO_(x) module 280 and revert to oxidation based regeneration by enabling the thermal management module 275.

Generally, the thresholds and threshold ranges discussed above are precalibrated according to desired performance and efficiency of the system. For the example, the thresholds and threshold ranges can be precalibrated to effectively achieve a high (e.g., maximum) soot burn rate and low (e.g., minimum) fuel consumption during a regeneration event on a particulate filter.

One embodiment of a method 500 for controlling the regeneration of a particulate filter (e.g., particulate filter 150) is shown in FIG. 7. In one implementation, the method 500 utilizes the above-described modules of the controller 130 to implement various actions or steps. However, in other implementations, the method 500 may utilize other modules or components not herein described to implement the various actions or steps. For reference, some of the actions of the method 500 will be described below as being implemented by the modules specifically enumerated herein.

As shown in FIG. 7, the method 500 begins by determining at 505 whether a regeneration trigger is set to ON. In one implementation, the regeneration module 260 is operable to monitor the condition of the system 100, and set the regeneration trigger to ON when the monitored conditions suggest the filter requires regeneration. If the filter does not require regeneration, then the trigger will remain set to OFF and the method 500 ends. However, if the regeneration trigger is set to ON as determined at 505, then the method 500 proceeds to operate the engine system 100 in a thermal management mode at 510 to effectuate at least a partial oxidation regeneration of the filter. Operation of the engine system 100 in the thermal management mode can be controlled by the thermal management module 275 as described above.

After initiating operation of the engine system in the thermal management mode, the method 500 determines at 515 whether at least one first operating condition downstream of the oxidation catalyst of the engine system has met an associated threshold. If the at least one first operating condition has not met its associated threshold, then the method 500 continues to operate the engine system in the thermal management mode at 510. However, if the at least one first operating condition has met its associated threshold, then the method 500 proceeds to cease operation of the engine system in the thermal management mode at 520. Essentially, while the engine system is operating in the thermal management mode at 510, the method 500 continuously determines whether the at least one first operating condition has been met. In some implementations, the at least one first operating condition includes two first operating conditions and associate thresholds: (1) the oxidation catalyst outlet exhaust temperature exceeding an associated temperature threshold for a predetermined amount of time; and (2) a filter outlet exhaust temperature exceeding an associated temperature threshold (e.g., target temperature). In one implementation, both first operating conditions must meet their respective thresholds for the determination at 515 to be answered affirmatively. In contrast, in another implementation, only one of the first operating conditions must meet its respective threshold for the determination at 515 to be answered affirmatively.

After ceasing operation of the engine system in the thermal management mode at 520 in view of an affirmative answer at 515, the method 500 determines whether operation of the engine system in a high NO_(x) mode would be appropriate, beneficial, or desirable at 530 for effective noxidation regeneration. If the decision at 530 is answered affirmatively, then the method 500 proceeds to operate the engine system in the high NO_(x) mode at 535. According to one implementation, operation in the high NO_(x) mode would be appropriate if (1) a minimum temperature associated with a NO₂ to NO_(x) ratio of at least a threshold ratio, or an oxidation catalyst outlet NO₂ flux is greater than a predetermined above-normal NO₂ flux; and (2) the product of an estimated amount of NO_(x) in the high NO_(x) mode and the NO_(x) reduction efficiency of the SCR catalyst is less than the maximum amount of tailpipe NO_(x) exiting the system allowed during regeneration as described above. If, however, the decision at 530 is negative (i.e., operation in the high NOx mode is not appropriate), the method 500 essentially bypasses operation of the engine system in the high NO_(x) mode and proceeds to determine at 550 whether the regeneration event should continue (by reverting back, if necessitated by the fourth operating conditions, to operation in the thermal management mode to raise the temperature again and create oxidation regeneration conditions) or stop.

It is noted that noxidation regeneration may still occur while the regeneration event is triggered even though the engine system 100 is not operating in the high NO_(x) mode (i.e., operation in the high NO_(x) mode is not appropriate). In other words operation in the high NO_(x) mode is not required for noxidation regeneration to occur. For example, as discussed above, as soon as operation in the thermal management mode is ceased at 520, the NO₂ in the exhaust gas will increase (and noxidation regeneration will occur) because there is less UHC passing through the DOC. Additionally, after operation in the thermal management mode is stops at 520, the artificially increased exhaust temperature is high enough that even small amounts of NO₂ in the exhaust gas, as well as some O₂ in the exhaust gas, will induce noxidation regeneration. Accordingly, operation in the high NO_(x) mode is not required for noxidation regeneration to occur, but operation in the high NO_(x) mode is used to accelerate noxidation regeneration. Therefore, in some implementations, after operation of the engine system in the thermal management mode ceases 520, such as when the DOC outlet temperature threshold is met for a predetermined amount of time, regeneration of the particulate filter continues (i.e., regeneration remains triggered) without operating the engine system in the high NO_(x) mode. In other words, while a regeneration event is triggered, the engine system can switch from a thermal management mode to a non-thermal management mode (which in some implementations is a high NO_(x) mode, and in other implementations is a mode other than a high NO_(x) mode).

Assuming operation in the high NO_(x) mode is determined to be appropriate at 530, then the method 500 proceeds to operate the engine system in the high NO_(x) mode at 535 to produce excess NO_(x) for accelerated noxidation regeneration of the filter. After initiating operation of the engine system in the high NO_(x) mode, the method 500 determines at 540 whether at least one second operating condition of the engine system has met an associated threshold. If the at least one second operating condition has not met its associated threshold, then the method 500 continues to operate the engine system in the high NO_(x) mode at 535. However, if the at least one second operating condition has met its associated threshold, then the method 500 proceeds to cease operation of the engine system in the high NO_(x) mode at 545. Essentially, while the engine system is operating in the high NO_(x) mode at 535, the method 500 continuously determines whether the at least one second operating condition has been met. In some implementations, the at least one second operating condition includes two second operating conditions and associated thresholds, such as: (1) the bed temperature of the oxidation catalyst 140 is less than a minimum threshold; and (2) the system is operating within a predetermined oxidation catalyst inlet exhaust temperature range, an exhaust flow rate range, and a particulate filter bed temperature range. In one implementation, both second operating conditions must meet their respective thresholds for the determination at 540 to be answered affirmatively. In contrast, in another implementation, only one of the second operating conditions must meet its respective threshold for the determination at 540 to be answered affirmatively.

After ceasing operation of the engine system in the high NO_(x) mode at 545 in view of an affirmative answer at 540, the method 500 determines whether at least one third operating condition of the engine system has met an associated threshold at 550. If the decision at 550 is answered affirmatively, then the method 500 sets the regeneration event trigger to OFF at 555 to stop the regeneration event on the particulate filter and the method ends. In some implementations, the at least one third operating condition includes three third operating conditions and associated thresholds, such as: (1) the amount of accumulation on the filter falls below an accumulation load lower threshold; (2) regeneration of the filter has been triggered for more than a time threshold as discussed above; and (3) the monitored burn rate is below a minimum threshold. In one implementation, all three of the third operating conditions must meet their respective thresholds for the determination at 550 to be answered affirmatively. In contrast, in another implementation, only one or two of the third operating conditions must meet its respective threshold for the determination at 550 to be answered affirmatively.

If the decision at 550 is answered negatively, then the method 500 proceeds to determine at 560 whether at least one fourth operating condition has met a corresponding fourth threshold. If the decision at 560 is answered negatively, then the method 500 reverts back to operating the engine system in the thermal management mode at 510. However, if the decision at 560 is answered positively, then the method 500 reverts back to determining whether operation in the high NO_(x) mode is appropriate at 530. Generally, the determination at 560 decides whether the conditions of the engine system are conducive to returning to operation in a thermal management mode to artificially increase the exhaust temperature for oxidation regeneration to occur, or whether conditions are not conducive to operation in the thermal management mode and checking to see if operation in the NO_(x) mode for noxidation regeneration should occur is more appropriate. In some implementations, the at least one fourth operating condition includes several conditions and associated thresholds, such as: (1) the DOC outlet or DPF inlet exhaust temperature is below a minimum temperature threshold associated with noxidation (e.g., between 300° C. and 320° C.); (2) the exhaust gas flow is above a minimum flow threshold; and (3) the engine operating point is within a calibrated permissible region of an engine speed-torque map. In one implementation, all three of the fourth operating conditions must meet their respective thresholds for the determination at 560 to be answered positively. In contrast, in another implementation, only one or two of the fourth operating conditions must meet its respective threshold for the determination at 560 to be answered positively.

The schematic flow chart diagrams and method schematic diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of representative embodiments. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the methods illustrated in the schematic diagrams. Additionally, the format and symbols employed are provided to explain the logical steps of the schematic diagrams and are understood not to limit the scope of the methods illustrated by the diagrams. Although various arrow types and line types may be employed in the schematic diagrams, they are understood not to limit the scope of the corresponding methods. Indeed, some arrows or other connectors may be used to indicate only the logical flow of a method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of a depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

Many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by various types of processors. An identified module of computer readable program code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module.

Indeed, a module of computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. Where a module or portions of a module are implemented in software, the computer readable program code may be stored and/or propagated on in one or more computer readable medium(s).

The computer readable medium may be a tangible computer readable storage medium storing the computer readable program code. The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

More specific examples of the computer readable medium may include but are not limited to a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), an optical storage device, a magnetic storage device, a holographic storage medium, a micromechanical storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, and/or store computer readable program code for use by and/or in connection with an instruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signal medium. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electrical, electro-magnetic, magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport computer readable program code for use by or in connection with an instruction execution system, apparatus, or device. Computer readable program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, Radio Frequency (RF), or the like, or any suitable combination of the foregoing

In one embodiment, the computer readable medium may comprise a combination of one or more computer readable storage mediums and one or more computer readable signal mediums. For example, computer readable program code may be both propagated as an electro-magnetic signal through a fiber optic cable for execution by a processor and stored on RAM storage device for execution by the processor.

Computer readable program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

What is claimed is:
 1. An apparatus for controlling the regeneration of a particulate filter of an exhaust aftertreatment system of an internal combustion engine system; comprising: an operating conditions module configured to monitor at least one condition of the internal combustion engine system; a regeneration module configured to trigger a regeneration event if the at least one condition of the internal combustion engine system meets a threshold; a thermal management module configured to operate the internal combustion engine system in a thermal management mode for a first time period while a regeneration event is triggered by the regeneration module; and a high NO_(x) module configured to operate the internal combustion engine system in a high NO_(x) mode for a second time period following the first time period while the regeneration event is triggered by the regeneration module.
 2. The apparatus of claim 1, wherein operation of the engine system in the thermal management mode results in oxidation regeneration of the particulate filter, and operation of the engine system in the high NO_(x) mode results in noxidation regeneration of the particulate filter.
 3. The apparatus of claim 1, wherein the length of the first time period is dependent on a temperature of the exhaust gas exiting an oxidation catalyst upstream of the particulate filter.
 4. The apparatus of claim 1, wherein the first time period ends when a temperature of the exhaust gas exiting an oxidation catalyst upstream of the particulate filter exceeds an oxidation catalyst outlet temperature threshold for a predetermined amount of time.
 5. The apparatus of claim 4, wherein the oxidation catalyst outlet temperature threshold comprises the difference between an oxidation catalyst outlet target temperature and an allowable temperature variation.
 6. The apparatus of claim 1, wherein the first time period ends when a temperature of the exhaust gas exiting the particulate filter exceeds a particulate filter outlet temperature threshold.
 7. The apparatus of claim 4, wherein the predetermined amount of time is less than 50% of the amount of time necessary to substantially completely regenerate the particulate filter via noxidation regeneration.
 8. The apparatus of claim 1, wherein the second time period is between approximately 90% and 98% longer than the first time period.
 9. The apparatus of claim 1, wherein the at least one condition of the internal combustion engine system comprises an amount of particulate matter accumulated on the particulate filter and the threshold comprises a maximum allowable amount of particulate matter accumulated on the particulate filter.
 10. The apparatus of claim 1, wherein the second time period begins after the first time period ends, when a temperature of exhaust gas exiting an oxidation catalyst upstream of the particulate filter is greater than a minimum temperature associated with a NO₂-to-NO_(x) ratio of at least a threshold ratio, and when a NO_(x) reduction efficiency of a selective catalytic reduction (SCR) catalyst is greater than a minimum efficiency threshold.
 11. The apparatus of claim 1, wherein the second time period begins after the first time period ends, when an estimate of the NO₂ flux exiting an oxidation catalyst upstream of the particulate filter exceeds an oxidation catalyst outlet NO₂ flux threshold, and when a NO_(x) reduction efficiency of a selective catalytic reduction (SCR) catalyst is greater than a minimum efficiency threshold.
 12. The apparatus of claim 1, wherein the second time period ends when a temperature of a bed of an oxidation catalyst upstream of the particulate filter drops below a minimum oxidation catalyst bed temperature.
 13. The apparatus of claim 12, wherein the minimum oxidation catalyst bed temperature is the bed temperature at which a predetermined minimum particulate matter burn rate from the particulate matter filter is achievable.
 14. The apparatus of claim 1, wherein the second time period ends when a temperature of the exhaust gas entering an oxidation catalyst upstream of the particulate filter is within a predetermined oxidation catalyst inlet exhaust temperature range, a flow rate of exhaust gas through the particulate filter is within a predetermined exhaust flow rate range, and a temperature of a bed of the particulate filter is within a predetermined particulate filter bed temperature range.
 15. The apparatus of claim 1, wherein the thermal management module is configured to operate the internal combustion engine system in the thermal management mode for a third time period following the second time period while the regeneration event is triggered by the regeneration module, wherein the triggered regeneration event is untriggered when an amount of particulate matter accumulated on the particulate filter is less than a minimum particulate matter accumulation threshold.
 16. The apparatus of claim 1, wherein the thermal management module is configured to operate the internal combustion engine system in the thermal management mode for a third time period following the second time period while the regeneration event is triggered by the regeneration module, wherein the triggered regeneration event is untriggered when the regeneration event has been triggered for more than a predetermined time threshold.
 17. The apparatus of claim 1, wherein the high NO_(x) module is further configured to operate the internal combustion engine system in the high NO_(x) mode for a third time period separate from the first and second time periods while a regeneration event is not triggered by the regeneration module.
 18. A method for controlling the regeneration of a particulate filter of an internal combustion engine system, comprising: triggering a regeneration of the particulate filter; operating the internal combustion engine system in a thermal management mode if a regeneration of the particulate filter has been triggered and while an at least one first operating condition has not met an at least one first threshold; switching operation of the internal combustion engine system from the thermal management mode to a high NO_(x) mode if the regeneration of the particulate filter remains triggered and when the at least one first operating condition meets the at least one first threshold; operating the internal combustion engine system in the high NO_(x) mode while an at least one second operating condition has not met an at least one second threshold; and ceasing operation of the internal combustion engine system in the high NO_(x) mode when the at least one second operating condition meets the at least one second threshold.
 19. The method of claim 18, further comprising switching operation of the internal combustion engine system from the high NO_(x) mode back to the thermal management mode after ceasing operation of the internal combustion system in the high NO_(x) mode and when at least one third operation condition has met a third threshold.
 20. An internal combustion engine system having an internal combustion engine, comprising: an oxidation catalyst in exhaust receiving communication with the internal combustion engine; a particulate filter downstream from the oxidation catalyst, the particulate filter being in exhaust receiving communication with the oxidation catalyst; and a controller comprising: a regeneration module configured to initiate a regeneration event on a particulate filter; a thermal management module configured to control the regeneration event according to a thermal management mode; a high NO_(x) module configured to control the regeneration event according to a high NO_(x) mode; and a switch module configured to monitor operating conditions of the internal combustion engine system during the regeneration event and to selectively switch between first and second regeneration states during the regeneration event, the first regeneration state comprising enablement of the thermal management module and disablement of the high NO_(x) module, and the second regeneration state comprising disablement of the thermal management module and enablement of the high NO_(x) module.
 21. The internal combustion engine system of claim 19, wherein the switch module switches from the first regeneration state to the second regeneration state when excess oxidation catalyst out NO₂ will not result in excess tailpipe out NO_(x). 